Beam shaping is essential in many lighting applications. Examples of beam shaping optical elements include classical elements such as reflectors and collimators. Such optical elements occupy a rather large volume and are relatively expensive, especially when an array of such optics is needed, as is often the case for spot lighting applications.
Beam shaping is generally used to reshape the output light profile of LEDs, because they have a very small and bright light output area, whereas a larger light output area is desired by users.
For LED spot lighting applications, the light emitted by an LED has to be collected and collimated to a certain degree. The degree of collimation depends on the application, but typically varies from 40° for a wide beam to 10° for a narrow beam.
For the collection and collimation functions, total internal reflection (TIR) collimators are typically used. They use a combination of refraction at a central part of the collimator and total-internal-reflection at the outer part of the collimator. Such collimators are relatively bulky and expensive.
The use of thin film micro-optics is being investigated widely as an alternative option for providing the same functionality as TIR collimators. These take the form of a slab of material which has microstructured surfaces on one or both surfaces.
For most applications, a single LED does not provide enough light. In that case, an array of LEDs is used, each with its own collimator. When using conventional optics, this option is not only costly but also, from a customer perspective, results in a shower-head impression when looking towards or into the light source. This shower-head impression is not appreciated from an aesthetic point of view.
The tiling of thin-film micro-optics does not have these drawbacks, in that the tiled structure has a generally planar appearance. However, there remain difficulties in achieving a small beam spread in combination with a high optical efficiency.
The invention aims to address this issue.
JP2002352611A discloses a display device comprising an array of beam shaping units arranged in a general plane, each beam shaping unit comprising a central refractive area S and one outer area M providing TIR.